Propellant for firearms is a chemical substance that produces gas when ignited, creating pressure that propels a bullet out of the barrel. The most common type of propellant used in modern firearms is smokeless powder, which is more efficient and produces less smoke than traditional black powder. When the trigger is pulled, a firing pin strikes a primer, igniting the propellant. This rapid combustion generates high-pressure gas, forcing the bullet down the barrel and out of the firearm. Proper selection and handling of propellant are crucial for safety and performance in shooting activities.